How the Test is Performed

How to Prepare for the Test

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

Your health care provider may recommend this test if you have signs or symptoms of paroxysmal nocturnal hemoglobinuria (PNH) or hemolytic anemia of unknown cause. Hemolytic anemia is a condition in which red blood cells die before they should. PNH red blood cells are very likely to be harmed by the body's "complement system." The complement system are proteins that move through the bloodstream. These proteins work with the immune system.

Normal Results

A normal test result is called a negative result. A normal result shows that less than 5% of red blood cells break down when tested. This breakdown is called hemolysis.

A negative test does not rule out PNH. False-negative results may occur if the fluid part of blood (serum) lacks complement.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

A positive test result means the results are abnormal. In a positive test, more than 10% of red blood cells break down. It could indicate the person has PNH.

Certain conditions can make the test results appear positive (called "false positive"). These conditions are autoimmune hemolytic anemias and leukemia.

Risks

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

Information developed by A.D.A.M., Inc. regarding tests and test results may not directly correspond with information provided by UCSF Medical Center. Please discuss with your doctor any questions or concerns you may have.